This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-372940, filed Dec. 6, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical disc drive for recording data on an optical disc and reproducing data recorded on the optical disc by irradiating it with a laser beam, and also to a signal processing method in the optical disc drive.
2. Description of the Related Art
In recent years, optical disc drives that record data on an optical disc and reproduce data recorded on the optical disc by irradiating the optical disc with a laser beam have been extensively studied and developed. In an optical disc drive, signals are detected using the sample and hold technique during a recording period (so-called mark period) in which data is recorded on the disc, and a reproduction period (so-called space period) between neighboring recording pulses. More specifically, a monitor signal indicating the amount of light emitted by a laser is detected to control the amount of a laser beam, and an error signal obtained from light reflected by the optical disc during the reproduction period is detected to control focusing and tracking.
However, signal detection precision suffers problems as the speed of the optical disc drive increases. Upon detecting a monitor signal that indicates the amount of light emitted by the laser, the mark and space levels are detected respectively. Upon detecting an error signal, the space level alone is detected. With increasing speed of the optical disc drive, the monitor and error signals cannot be detected in time, thus causing detection errors. Consequently, the laser light amount control or servo control precision impairs.
It is an object of the present invention to provide an optical disc drive and signal processing method that can assure high signal detection precision.
(1) An optical disc drive according to an aspect of the present invention comprises an emitting section configured to emit a disc with a laser beam, a light-receiving section configured to receive the laser beam emitted by the emitting section, a converting section configured to convert the laser beam received by the light-receiving section into an electrical signal, a slewing rate control section set after the converting section and configured to generate a slewing rate control signal in accordance with a rotational velocity of the disc, and reducing a change in amplitude of the electrical signal on the basis of the slewing rate control signal, and a signal processing section configured to process the electrical signal controlled by the slewing rate control section.
(2) A signal processing method according to an aspect of the present invention comprises the steps of receiving light, converting the received light into an electrical signal, and processing the electrical signal using a slewing rate control signal.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.